Added knockout.rx definitions

RxJS-Knockout binding <https://github.com/Igorbek/knockout.rx>

knockout.rx/knockout.rx-tests.ts

@@ -0,0 +1,12 @@
+/// <reference path="knockout.rx.d.ts"/>
+
+var ax: Rx.IObservable<number>;
+
+var ao = ax.toKoObservable();
+
+ao(100);
+ao.getSubscriptionsCount();
+
+ao.toObservable();
+ao.toObservable("change");
+ao.toObservable<Error>("error");

knockout.rx/knockout.rx.d.ts

@@ -0,0 +1,14 @@
+/// <reference path="../knockout/knockout.d.ts"/>
+/// <reference path="../rx.js/rx.js.d.ts"/>
+
+interface KnockoutSubscribableFunctions<T> {
+	toObservable(event?: string): Rx.IObservable<T>;
+	toObservable<TEvent>(event: string): Rx.IObservable<TEvent>;
+}
+
+declare module Rx {
+	interface IObservable<T> {
+		toKoSubscribable(): KnockoutSubscribable<T>;
+		toKoObservable(initialValue?: T): KnockoutObservable<T>;
+	}
+}